Interactive anatomical mapping and estimation of anatomical mapping quality

ABSTRACT

A method includes receiving an anatomical mapping that includes multiple measurements acquired at multiple respective locations within an organ of a patient. An estimated surface of the organ is computed based on the measurements. A three-dimensional (3D) shell of the organ, which extends inwards from the estimated surface of the organ and has a predefined thickness, is defined. A quality of the anatomical mapping is estimated based on the measurements whose locations fall within the 3D shell.

FIELD OF THE INVENTION

The present invention relates generally to anatomical mapping, andparticularly to methods and systems for interactive anatomical mappingand estimation of anatomical mapping quality.

BACKGROUND OF THE INVENTION

Anatomical mapping may be used for diagnosing various types of medicalconditions, such as cardiac arrhythmia. Various techniques may beapplied for deriving an anatomical mapping and for controlling themapping procedure.

For example, U.S. Pat. No. 8,744,566, whose disclosure is incorporatedherein by reference, describes methods and systems for the determinationand representation of anatomical information. The methods and systemsinclude generating anatomical information of the heart, based onpositions of the catheter electrodes and the electrical signals from theelectrodes at the determined subset of electrode positions.

U.S. Pat. No. 8,457,371, whose disclosure is incorporated herein byreference, describes method and apparatus for mapping a structure. Themapping apparatus may include one or more electrodes that can sense avoltage that can be correlated to a three dimensional location of theelectrode at the time of the sensing or measurement. A map of an area orvolume can be determined based upon the sensing of the plurality ofpoints without the use of an imaging device. An implantable medicaldevice can then be navigated relative to the mapping data.

U.S. Pat. No. 8,900,225, whose disclosure is incorporated herein byreference, describes a method for performing a medical procedure thatincludes bringing a probe into contact with an organ in a body of apatient. A map of the organ is displayed, and the location of the proberelative to the map is tracked.

U.S. Patent Application Publication 2009/0099468, now abandoned, whosedisclosure is incorporated herein by reference, describes a method, anapparatus, and a computer program product for automated processing ofintra-cardiac electrophysiological data. The method includes recordingelectro-gram data, defining at least one reference channel containing areference beat for determining temporal locations, creating an index ofthe temporal locations, analyzing in real-time at least oneelectrophysiological feature, and providing an updated index and resultsof the analysis.

SUMMARY OF THE INVENTION

An embodiment of the present invention that is described herein providesa method including receiving an anatomical mapping that includesmultiple measurements acquired at multiple respective locations withinan organ of a patient. An estimated surface of the organ is computedbased on the measurements. A three-dimensional (3D) shell of the organ,which extends inwards from the estimated surface of the organ and has apredefined thickness, is defined. A quality of the anatomical mapping isestimated based on the measurements whose locations fall within the 3Dshell.

In some embodiments, defining the 3D shell includes forming, at apredefined distance inwards from the estimated surface, a virtualsurface confining the shell between the estimated surface and thevirtual surface. In other embodiments, estimating the quality of theanatomical mapping includes counting a number of the measurements whoselocations fall within at least part of the shell. In yet otherembodiments, the shell includes multiple volume pixels (voxels), andestimating the quality is based on a number of the voxels, within the atleast part of the shell, in which the measurements fall.

In an embodiment, the shell includes a surface including multiplepixels, and estimating the quality is based on a number of the pixels,within the at least part of the shell, in which the measurements fall.In another embodiment, the organ includes a cavity of a heart.

There is additionally provided, in accordance with another embodiment ofthe present invention, a method including receiving a partial anatomicalmapping that includes multiple measurements acquired at multiplerespective locations within an organ of a patient. An estimated partialsurface of the organ is computed based on the measurements. Based on themeasurements, an unvisited region of the organ, which was not yet mappedby the partial anatomical mapping, is identified. The unvisited regionis indicated to a user, so as to assist the user in mapping theunvisited region and extending the estimated partial surface.

In some embodiments, the multiple measurements are acquired using adistal end of a catheter, and indicating the unvisited region includesdisplaying a graphical indication indicative of a direction to which theuser is to move the distal end in order to map the unvisited region. Inother embodiments, the method includes overlaying a grid of volumepixels (voxels) within at least part of the organ, and identifying theunvisited region includes identifying one or more voxels of the gridthat were not yet mapped by the partial anatomical mapping. In yet otherembodiments, the method includes defining a given volume that extendsoutwards from a catheter distal end that is used for acquiring themeasurements, and identifying the unvisited region includes identifying,within the given volume, locations that were not yet visited by thedistal end.

There is additionally provided, in accordance with an embodiment of thepresent invention, an apparatus including an interface and a processor.The processor is configured to receive from the interface an anatomicalmapping, including multiple measurements acquired at multiple respectivelocations within an organ of a patient, to compute an estimated surfaceof the organ based on the measurements, to define a three-dimensional(3D) shell of the organ, which extends inwards from the estimatedsurface of the organ and has a predefined thickness, and to estimate aquality of the anatomical mapping, based on the measurements whoselocations fall within the 3D shell.

There is further provided, in accordance with an embodiment of thepresent invention, an apparatus including an interface and a processor.The processor is configured to receive a partial anatomical mapping,including multiple measurements acquired at multiple respectivelocations within an organ of a patient, to compute an estimated partialsurface of the organ based on the measurements, to identify, based onthe measurements, an unvisited region of the organ that was not yetmapped by the partial anatomical mapping, and to indicate on the outputdevice the unvisited region to a user, so as to assist the user inmapping the unvisited region and extending the estimated partialsurface.

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, pictorial illustration of a catheter-basedtracking and ablation system that employs anatomical mapping, inaccordance with an embodiment of the present invention;

FIG. 2 is a schematic, pictorial illustration of an anatomical map of aninner surface of a heart, and a visualization scheme that directs a usertoward unmapped areas of the surface, in accordance with an embodimentof the present invention;

FIG. 3 is a schematic, pictorial illustration of an estimated anatomicalmap of an inner surface of a heart, in accordance with an embodiment ofthe present invention; and

FIG. 4 is a schematic, pictorial illustration of a scheme for estimatingthe quality of an anatomical map, in accordance with an embodiment ofthe present invention.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

In some medical procedures, such as cardiac ablation, a medical probe isnavigated into a patient heart based on an estimated anatomical map ofthe heart. Estimating the anatomical map may be carried out by insertinga catheter having sensing electrodes disposed on its distal end, andmeasuring certain signals at multiple locations of tissue on the heartinner surface using the electrodes. Mapping algorithms that are based onsuch measurements, such as fast anatomical mapping (FAM), are known inthe art. The FAM method may provide a physician with additional mappingcapabilities, such as electro-physiological (EP) mapping that may beused for the cardiac ablation.

During the FAM procedure, a physician navigates the distal end of thecatheter to desired locations distributed across the tissue in questionso as to collect anatomical signals therefrom. In principle, the FAM mayprovide the physician with a surface representing an estimatedanatomical mapping of the tissue in question. This surface will be usedby the physician during the EP mapping and ablation procedures,therefore it is important to monitor the quality of the anatomicalmapping before starting the EP procedure.

Embodiments of the present invention that are described hereinbelowprovide improved techniques for interactive anatomical mapping. Thedisclosed techniques may be used for indicating to the physicianunmapped (“unvisited”) regions of the heart surface. In an embodiment,after receiving partial measurements of the anatomical mapping, theprocessor computes a partial surface of the tissue and identifies, basedon the partial surface, one or more unvisited regions in the tissue forfurther anatomical mapping.

In an embodiment, the processor is configured to display a graphicalindication that directs the physician to the unvisited regions, so as toassist the physician in mapping the entire surface. After concluding theanatomical mapping, the processor displays the estimated anatomicalmapping of the entire surface.

In another embodiment, the processor is configured to estimate thequality of the anatomical mapping by defining a three-dimensional (3D)shell which extends inwards from the estimated anatomical surface. Forexample, the processor may define a virtual surface parallel to theestimated surface so that the 3D shell is the volume confined betweenthe two surfaces. In some embodiments, the processor estimates thequality of the anatomical mapping based on the number of mappingmeasurements whose locations fall within the predefined volume.

The disclosed techniques provide real-time visualization of the ongoingmapping procedure, and provides feedback regarding the quality of theestimated anatomical surface, thereby obtaining high quality mapping andshortening the procedure cycle time.

System Description

FIG. 1 is a schematic, pictorial illustration of a catheter-basedtracking and ablation system 20, in accordance with an embodiment of thepresent invention. System 20 comprises a catheter 22, in the presentexample a cardiac catheter, and a control console 24. In the embodimentdescribed herein, catheter 22 may be used for any suitable therapeuticand/or diagnostic purposes, such as anatomical mapping of a cavity 37 ina heart 26.

Console 24 comprises a processor 39, typically a general-purposecomputer, with suitable front end and interface circuits 38 forreceiving signals via catheter 22 and for controlling the othercomponents of system 20 described herein. Console 24 further comprises auser display 35, also referred to as an output device, which isconfigured to display tools for assisting in anatomical mapping as shownin FIGS. 2-4 below.

The procedure of anatomical mapping is carried out using distal end 40that collects multiple measurements at respective locations of the hearttissue, the measurements outcomes are referred to herein as map points.Each map point comprises a three-dimensional (3D) coordinate on thetissue of cavity 37 and a respective measurement of some physiologicalproperty that is measured at this coordinate.

In some embodiments, processor 39 is configured to construct, based onthe measurements or map points, an estimated anatomical surface (shownin FIGS. 3 and 4), and present the estimated anatomical surface tophysician 30 on display 35. In constructing the estimated anatomicalsurface, processor 39 may apply to the measurements a procedure such asthe Fast Anatomical Mapping (FAM) procedure, which is described, forexample, in U.S. Patent Application Publication 2011/0152684, whosedisclosure is incorporated herein by reference.

In some medical procedures, such as ablation of tissue, physician 30creates an anatomical map of the tissue to be ablated in advance. Toperform the anatomical mapping, physician 30 inserts catheter 22 throughthe vascular system of a patient 28 lying on a table 29. Catheter 22comprises one or more electrodes (not shown) typically fitted at adistal end 40. The electrodes are configured to sense the tissue ofcavity 37 of heart 26. Physician 30 navigates distal end 40 into cavity37 by manipulating catheter 22 with a manipulator 32 near the proximalend of the catheter as shown in an inset 23. The proximal end ofcatheter 22 is connected to interface circuitry in processor 39.

In some embodiments, the position of the distal end in cavity 37 ismeasured by a position sensor (not shown) of a magnetic positiontracking system. The measured position serves as the coordinate of therespective map point.

For example, the anatomical measurements may be acquired using the fastanatomic mapping (FAM) functions of the CARTO® 3 System cooperativelywith a mapping catheter such as the Navistar® Thermocool® catheter, bothavailable from Biosense Webster, Inc., 3333 Diamond Canyon Road, DiamondBar, Calif. 91765.

In this case, console 24 comprises a driver circuit 34, which drivesmagnetic field generators 36 placed at known positions external topatient 28 lying on table 29, e.g., below the patient's torso. Theposition sensor is fitted to the distal end, and configured to generateposition signals in response to sensed external magnetic fields fromfield generators 36. The position signals are indicative of the positionthe distal end in the coordinate system of the position tracking system.

This method of position sensing is implemented in various medicalapplications, for example, in the CARTO™ system, produced by BiosenseWebster Inc. (Diamond Bar, Calif.) and is described in detail in U.S.Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and6,332,089, in PCT Patent Publication WO 96/05768, and in U.S. PatentApplication Publications 2002/0065455 A1, 2003/0120150 A1 and2004/0068178 A1, whose disclosures are all incorporated herein byreference.

In some embodiments, physician 30 may use processor 39 for navigatingdistal end 40 to a target location and for activating the electrodes soas to sense and/or ablate the tissue at cavity 37. In alternativeembodiments, processor 39 may be used only for assisting physician 30 inmapping unvisited regions and in estimating the quality of theanatomical mapping.

Processor 39, typically comprises a general-purpose computer, which isprogrammed in software to carry out the functions described herein. Thesoftware may be downloaded to the computer in electronic form, over anetwork, for example, or it may, alternatively or additionally, beprovided and/or stored on non-transitory tangible media, such asmagnetic, optical, or electronic memory.

Interactive Anatomical Mapping by Indicating Unvisited Regions

FIG. 2 is a schematic, pictorial illustration of an anatomical map 41 ofcavity 37 and a visualization scheme that directs physician 30 towardunmapped areas of cavity 37, in accordance with an embodiment of thepresent invention. In some embodiments, processor 39 receives anatomicaldata of heart 26 and uses the anatomical data to display an estimatedvolume 42 of cavity 37 in heart 26. In an embodiment, volume 42 may bedisplayed schematically as a cubical shape, or using any other suitableshape.

In some embodiments, processor 39 further receives from distal end 40partial anatomical mapping, comprising multiple measurements, such asfast anatomical mapping (FAM), acquired at multiple respective locationswithin cavity 37. In an embodiment, based on these measurements,processor 39 is configured to compute an estimated partial surface 46that was already mapped in cavity 37.

In an embodiment, using estimated volume 42 and the measurements alreadyacquired, processor 39 is further configured to identify an unvisitedregion of cavity 37, such as an estimated surface 44, which was not yetmapped by the partial anatomical mapping. In the present context, theterm “unvisited region” refers to regions of the surface of cavity 37that are not yet represented by estimated partial surface 46.

In some embodiments, processor 39 displays on anatomical map 41 theposition of distal end 40 as received from the position tracking system,and an arrow 48 that indicates the direction of the unvisited region, soas to assist physician 30 to complete the mapping of the tissue ofcavity 37.

In other embodiments, processor 39 overlays a grid of three-dimensional(3D) pixels, also known as voxels (not shown), over volume 42. In thisembodiment, processor 39 samples part of the voxels within volume 42 andidentifies the voxels not yet visited by distal end 40. Then, processor39 displays arrow 48 that indicates the direction of the unvisitedvoxels.

In some embodiments, processor 39 may display surface 44 of theunvisited region based on the measurements acquired at surface 46 andvolume 42. In other embodiments, processor may display only surface 46,distal end 40, and arrow 48 so as to indicate the direction of theunvisited region to physician 30 without extrapolating the measurementsacquired for estimating surface 46.

In an embodiment, processor 39 defines a given volume (not shown) thatextends outward from distal end 40 and identifies locations within thegiven volume that were not yet visited by distal end 40. Then, processor39 displays arrow 48 that indicates the direction of the unvisitedlocations within the given volume, so as to assist physician 30 tocomplete the mapping of the tissue of cavity 37.

Estimating the Quality of the Anatomical Mapping

FIG. 3 is a schematic, pictorial illustration of an estimated anatomicalmap 43, in accordance with an embodiment of the present invention. Insome embodiments, for generating anatomical map 43, processor 39receives multiple anatomical measurements, such as fast anatomicalmapping (FAM), acquired at multiple respective locations within cavity37.

Based on the measurements, processor 39 computes an estimated surface 45and displays surface 45 in anatomical map 43 on display 35. Note thatthe computation of surface 45 is based on sampling measurements ratherthan continuous mapping of surface 45. In some embodiments, thecomputation of surface 45 may involve interpolation of the samplingmeasurements acquired therein, therefore, at least parts of surface 45as displayed in map 43 may be inaccurate. For example, an interpolatedregion between multiple measurements may comprise an unvisitedanatomical feature (e.g., bump or crater) that may deviate from theestimated topography made by processor 39.

In some embodiments, physician 30 may define a 3D shell 52 that extendsinwards from estimated surface 45 into the internal volume of cavity 37.The shape of shell 52 may be defined by processor 39 using variousmethods. For example, processor 39 defines a virtual surface 50 parallelto surface 45 at a predefined distance (e.g., 7 mm) set by physician 30or by processor 39. In this embodiment, the volume of shell 52 isconfined between the boundaries of surfaces 45 and 50. In an embodiment,the volume of shell 52 is used for estimating the anatomical mappingquality of surface 45 as depicted in FIG. 4 below.

FIG. 4 is a schematic, pictorial illustration of a scheme for estimatingthe quality of anatomical map 43, in accordance with embodiments of thepresent invention. In some embodiments, processor 39 displays onanatomical map 43 surfaces 45 and 50, shell 52, and measurements 54acquired by visiting selected locations at surface 45, using distal end40 as described in FIGS. 1-3 above.

In some embodiments, processor 39 is configured to select within thevolume of shell 52 one or more slices, such as slices 56 and 58. Theslices may be selected randomly by processor 39, or according to apredefined parameter (e.g., specific locations within shell 52) setmanually by physician 30 or automatically by processor 39.

In an embodiment, each slice represents a subsurface or a sub-volumewithin shell 52 comprising multiple pixels. In the example of FIG. 4,each slice comprises nine pixels depicted for the sake of clarity. Inpractice, each slice may comprise any suitable number of pixels.

In some embodiments, each slice may comprise pixels 55 representingmeasurements 54 falling within the respective slice. In an embodiment,processor 39 is configured to check the portion of pixels 55 fallingwithin each slice so as to estimate the quality of the anatomicalmapping represented by surface 45. In an embodiment, insets 66 and 68represent the distribution of pixels 55 within slices 56 and 58,respectively. In general, a highly populated slice represents a highmapping quality and vice versa.

In inset 66, it appears that pixels 55 represent the majority of pixels(e.g., eight out of nine) of slice 56, therefore, slice 56 may get ahigh score (e.g., 89% (derived as 8/9=0.89) indicating high quality ofthe anatomical mapping on the left side of map 41. Using the samemethodology, only two pixels 55 fall within slice 58, and the score ofslice 58 is 22% (derived by counting 2 pixels out of 9), indicating lowquality of the anatomical mapping in the upper central region ofanatomical map 41.

In some embodiments, based on the scoring methodology described above,processor 39 is configured to display a quantitative map representingthe quality of the anatomical mapping for each region of cavity 37. Inan embodiment, physician 30 may set one or more quality thresholds sothat processor 39 provides physician 30 with alerts in case of lowerthan desired quality of the anatomical mapping at specific locations ofcavity 37. In other embodiments, slices 56 and 58 may representvolumetric elements rather than two-dimensional (2D) surfaces, so thatpixels 55 may represent voxels (not shown), rather than 2D pixels.

Although the embodiments described herein mainly address cardiologyapplications, the methods and systems described herein can also be usedin other applications, such as in ear-nose-throat (ENT), andbronchoscopy.

It will be appreciated that the embodiments described above are cited byway of example, and that the present invention is not limited to whathas been particularly shown and described hereinabove. Rather, the scopeof the present invention includes both combinations and sub-combinationsof the various features described hereinabove, as well as variations andmodifications thereof which would occur to persons skilled in the artupon reading the foregoing description and which are not disclosed inthe prior art. Documents incorporated by reference in the present patentapplication are to be considered an integral part of the applicationexcept that to the extent any terms are defined in these incorporateddocuments in a manner that conflicts with the definitions madeexplicitly or implicitly in the present specification, only thedefinitions in the present specification should be considered.

The invention claimed is:
 1. A method, comprising: receiving ananatomical mapping, comprising multiple measurements acquired atmultiple respective locations within an organ of a patient, the multiplemeasurements including a physiological property of the organ acquired byan electrode at the multiple respective locations, and 3-D coordinatesof the multiple respective locations; computing an estimated surface ofthe organ based on the measurements; defining a three-dimensional (3D)shell of the organ, which extends inwards from the estimated surface ofthe organ and has a predefined thickness; and estimating a quality ofthe anatomical mapping, based on the measurements whose locations fallwithin the 3D shell.
 2. The method according to claim 1, whereindefining the 3D shell comprises forming, at a predefined distanceinwards from the estimated surface, a virtual surface confining theshell between the estimated surface and the virtual surface.
 3. Themethod according to claim 1, wherein estimating the quality of theanatomical mapping comprises counting a number of the measurements whoselocations fall within at least part of the shell.
 4. The methodaccording to claim 3, wherein the shell comprises multiple volume pixels(voxels), and wherein estimating the quality is based on a number of thevoxels, within the at least part of the shell, in which the measurementsfall.
 5. The method according to claim 3, wherein the shell comprises asurface comprising multiple pixels, and wherein estimating the qualityis based on a number of the pixels, within the at least part of theshell, in which the measurements fall.
 6. The method according to claim1, wherein the organ comprises a cavity of a heart.
 7. Apparatus,comprising: an interface; and a processor, configured to receive fromthe interface an anatomical mapping, comprising multiple measurementsacquired at multiple respective locations within an organ of a patient,the multiple measurements including a physiological property of theorgan acquired by an electrode at the multiple respective locations, and3-D coordinates of the multiple respective locations, to compute anestimated surface of the organ based on the measurements, to define athree-dimensional (3D) shell of the organ, which extends inwards fromthe estimated surface of the organ and has a predefined thickness, andto estimate a quality of the anatomical mapping, based on themeasurements whose locations fall within the 3D shell.
 8. The apparatusaccording to claim 7, wherein the processor is configured to form, at apredefined distance inwards from the estimated surface, a virtualsurface confining the shell between the estimated surface and thevirtual surface.
 9. The apparatus according to claim 7, wherein theprocessor is configured to estimate the quality based on a number of themeasurements whose locations fall within at least part of the shell. 10.The apparatus according to claim 9, wherein the shell comprises multiplevolume pixels (voxels), and wherein the processor is configured toestimate the quality based on a number of the voxels, within the atleast part of the shell, in which the measurements fall.
 11. Theapparatus according to claim 9, wherein the shell comprises a surfacecomprising multiple pixels, and wherein the processor is configured toestimate the quality based on a number of the pixels, within the atleast part of the shell, in which the measurements fall.
 12. Theapparatus according to claim 7, wherein the organ comprises a cavity ofa heart.